Radio Bursts from Space

I recently reviewed a book about Carl Sagan’s interest in ancient aliens, written by Donald Zygutis (1). Early on in his illustrious career, Sagan expressed scepticism about seeking E.T. life using radio telescopes, instead advocating a search through historical accounts and myths to determine whether our planet had been visited (2). He argued that in a standard galaxy there are so many stars/planets etc, that all you’d need to do is point the radio receiver at any given galactic source beyond the Milky Way, and alien radio signals should come screaming out at you.

They generally don’t, of course, which led Sagan to the early logical conclusion that SETI’s search with radio telescopes was bound to fail. However, this approach became the only game in town, with serious funding at its disposal, and Sagan fell into line behind it – supporting this doomed search for E.T. radio signals ostensibly from stars within out galactic neighbourhood.

Decades on, and SETI has come up with little of any merit. The odd interesting blip, sure, but nothing demonstrably repetitive, or intelligent. Other searches have also come up empty-handed, including an extensive search for highly advanced galactic civilisations using infra-red (3), based upon the theories of the physicist Freeman Dyson. Looking for an infra-red signature from other galaxies seems like a bit of a stretch to me. Sagan’s initial premise about radio waves emanating from other distant galaxies is more plausible. By staring at the tiny amount of our sky that any given distant galaxy occupies, radio telescopes can cover a lot of possible stars in a very small space. If any of them contain radio-emitting alien species, shouting for attention, then we should pick them up one would have thought.

Which leads me to news of a scientific breakthrough in pinpointing repeated bursts of radio activity from a distant dwarf galaxy. A determined effort to locate the source of some Fast Radio Bursts, using the Very Large Array in New Mexico, has not only yielded the source (an innocuous little galaxy some 3 billion light years away (4, 5)) but also knocked out some reproducible science:

“In 83 hours of observing time over six months in 2016, the VLA detected nine bursts from FRB 121102. In addition to detecting the bright bursts from FRB 121102, the team’s observations also revealed an ongoing, persistent source of weaker radio emission in the same region.” (6)

Five more Fast Radio Bursts have been detected by the Green Bank Telescope in 2016, and one with the Arecibo Observatory, bringing the total number of these short, seemingly random emissions from FRB 121102 to seventeen in four years (7). They cover a broad range of radio frequencies. The co-ordinates of FRB 121102 are RA 05h31m55s Dec+33d08m (8) which is in the constellation Auriga near to the ‘Flaming Star Nebula’ IC 405 (9).

This begs the question, why aren’t SETI all over this? Isn’t this exactly the kind of thing Sagan spoke about? Instead, all of the scientists involved in this research seem desperate to find a natural explanation for this phenomenon – something more complex than Quasars, but not actually intelligent:

“We argue that a burst source associated with a low-luminosity active galactic nucleus or a young neutron star energizing a supernova remnant are the two scenarios for FRB121102 that best match the observed data.” (10)

and:

“Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.” (11)

It’s curious – all those decades searching for strong, repetitive radio signals, and when something turns up which fits the bill, Science – and SETI – get cold feet.

Of course, if this is intelligently-generated radio noise from an advanced civilisation in a distant galaxy, then it was emitted 3 billion years ago, give or take. Presumably, that civilisation is long since gone. But wouldn’t it be amazing if something intelligible could eventually be gleaned from this radio twitter, even if the source is now, to paraphrase John Cleese, an ex-extraterrestrial?

A Dark Star Solution?

Let’s go back to that nebula in the constellation Auriga. It is interesting to note that the proper motion of the central star of this reflection nebula can be traced back to Orion’s Belt (12). It did cross my mind that this nebula might have a Dark Star connection, given my current interest in a nebula shroud wrapped around this proposed outer solar system object (13). A sub-brown dwarf located at a very distant point in the outer solar system, wrapped up in an accreting nebula in interstellar space (14), could indeed have a magenta hue. Magenta is a possible colour along the sub-brown dwarf spectrum.

As tempting a proposition as this might be, there are problems that must be overcome here. For this to be the case, some crazy misidentification would have had to have taken place. The nebula is thought to reside some 1500 light years away. That’s on a completely different scale to a nebula-shrouding planet at inner Oort Cloud distances, meaning that calculations of the nebula’s distance would be stunningly inaccurate. The Flaming Star Nebula need not necessarily be what I’m looking for.

Let’s say, for the sake of argument, that a smaller, darker nebula is indeed cloaking an inner object in that direction, located relatively close to home, and that its detection is complicated by the coincidental presence of IC 405. Let us consider whether a planetary body orbiting this Dark Star object be the source of these FRBs.

Because many of these fast radio bursts occur outside of the galactic plane, they are thought to have an extragalactic source. So, because they’re uncommonly bright, these extragalactic distances imply an incredibly energetic source. Now, if the radio source was instead relatively local, the requirement for a massive amount of energy to create these bursts disappears. The bursts are also thought to emerge from, basically, a pinpoint region of the sky, but they are often not easily reproducible. FRB 121102 is an exception to this as further bursts have been detected over the course of several years (8).

Let’s speculate that the radio bursts comes from a planet in the Milky Way. Because of FRB 121102’s location in Auriga, the planet is not moving around a star located deep in the Milky Way, because it is not located on the galactic plane. Perhaps, then, it is located within our local galactic neighbourhood? Scientists looking at the spectra of radio waves have concluded that the ‘dispersion measure’ of the radio pulses is too great to have come from a local source. This is because the radio waves appear to have travelled through a significant amount of ionised plasma on their way to us:

“The burst [in this case that of FRB 110523] has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy.” (15).

It’s interesting to note that the presence of a dense nebula might create conditions (i.e. an abundant presence of ionised plasma) that could facilitate the dispersion measure effect seen in Fast Radio Pulses. Such a scenario offers a less exciting proposition than a cosmologically mysterious, highly energetic pulse emerging from a distant dwarf galaxy. Perhaps that’s why astrophysicists seem to favour the latter over the former.

Here’s a thought then. If there is a Dark Star in our own solar system, wrapped up in a highly localised, dense nebula of ionised plasma, which shrouds its emission of visible and infra-red light, then that nebula might provide an alternative explanation for the physics described. It might also explain why it’s tricky to repeat the science. After all, the bursts would be getting emitted from a planet orbiting the Dark Star. So, like the Galilean moons of Jupiter, the emitting world would be constantly changing its position in the sky, in an oscillating movement. It might even spend time behind the Dark Star itself, as it moves along its orbit, thus experiencing periods of radio silence from our viewpoint.

Again, this is simply speculation on my part. Most (all?) astronomers would have little interest in considering worlds within nebulae, because that’s simply not on their radar. But the idea of nebulae getting wrapped around free-floating worlds in interstellar space is central to my way of thinking right now. So, an association between these Dark Stars and enigmatic radio ‘signals’ from seemingly nowhere does not seem quite as strange as it would to mainstream scientists.